American telly shows.?

Okay so I was watching Californication the other day(love the series) and it just came to my mind outta nowhere and ever since I'm wondering - Do they actually air the adult version (if there IS any censored version, which I doubt), with nudity and all on prime time? Or is this channel, Showtime, some adult-ish channel or something? Because Dexter, The Borgias, and shameless's got nudity too and these also belong to the same channel, i guess. Thanx.